Transcript Chapter 1 Computer Basics

Chapter 3
Hardware
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Outline
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What's inside a system unit
Memory
Microprocessor
Input and Output Devices
Secondary storage devices
Booting process
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Objectives
• Identify the components in the system unit
and explain their functions.
• Differentiate between the various types of
memory.
• Explain how the CPU uses the four steps of
a machine cycle to process data.
• List the factors that affect CPU performance.
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Objectives
• Describe the types of expansion slots and
expansion cards in the system unit.
• List the components necessary to connect a
peripheral device to a computer and
describe each component’s role.
• List the commonly used I/O and secondary
storage devices.
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Objectives
• Describe factors that affect the quality of a
monitor.
• Explain how data are stored on a
floppy/hard disk.
• Differentiate between low-level formatting
and high-level formatting of a hard disk.
• Explain the startup process for a personal
computer.
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part 1
WHAT'S INSIDE A
SYSTEM UNIT?
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What’s inside?
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Integrated circuit
• Most of the components inside a computer are
integrated circuits, commonly called chips or
microchips.
• An integrated circuit (IC) is a thin slice of crystal
packed with microscopic circuit elements such as
wires, transistors, capacitors, and resistors.
• A chip is packaged in a ceramic carrier that
provides connectors to other computer
components. We can find lots of chips on the
motherboard.
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Main board
• Inside the system unit, chips are housed on a
circuit board called main board, system board or
mother board.
• If you look carefully at a computer circuit board
you'll see that some chips are soldered, that is
fused, to the board, but other chips are plugged
into the board and can be removed.
• Soldered chips are permanent and aren't likely to
work loose. Removable chips allow you to
upgrade your computer components.
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Main board
• In a microcomputer, the motherboard contains the
processor chip, the chips for computer memory,
and chips that handle basic input and output.
• Circuits etched into the motherboard act like wires,
providing a path so the computer can transport
data from one chip to another as needed for
processing.
• In addition, the motherboard contains expansion
slots that allow you to connect peripheral devices
to the computer.
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Data transport
• Typically, data travels from one location to
another within the computer on an electronic
pathway or circuit called a data bus.
• The data bus is a series of electronic circuits that
connect the various electrical elements on the
motherboard.
• The bus contains data lines and address lines. Data
lines carry the signals that represent data. Address
lines carry the location of data to help the
computer find the data that it needs to process.
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Data transport
• A computer data bus "picks up" a load of
bits from one of the components on the
motherboard, then transfers these bits to
another motherboard component. After
dropping off this load of bits, the bus
collects another load.
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part 2
MEMORY
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what is memory?
• Memory is electronic circuitry that holds
data and program instructions.
• There are three types of memory: random
access memory(RAM), read-only
memory(ROM) and CMOS memory. Each
type of memory is characterized by the kind
of data it contains and the technology it uses
to hold the data.
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RAM
• Random access memory (RAM) chips hold
the program and data that the CPU is
presently processing. That is, it is temporary
or volatile storage.
• RAM speed is often measured in
nanosecond, that is, one billionth of a
second. RAM speed can be 60 nanoseconds,
or 70, 80.
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Why is RAM so important?
• RAM is the "waiting room" for the
computer's processor. RAM holds raw data
that is waiting to be processed. RAM holds
the instructions that will process the raw
data. RAM also holds processed data before
it is stored more permanently on disk or
tape.
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RAM is a waiting room
display
store
print
process
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Why is RAM so important?
• In addition to data and software instructions,
RAM holds operating system instructions
that control the basic functions of the
computer system. These instructions are
loaded into RAM every time you start your
computer and remain there until you turn
the computer off.
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Address Space
• Data are transferred to and from memory in
groups of bits (bit, byte and so on) called
words.
• To access a word in memory requires an
identifier. In the hardware level, each word
is identified by an address.
• The total number of uniquely identifiable
locations in memory is called the address
space.
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Virtual memory
• With virtual memory, large programs are divided
into parts which can be stored on a secondary
storage device, usually a hard disk. Each part is
read into RAM only when needed. In this way,
computer systems are able to run very large
programs.
• Virtual memory is not as fast as RAM because the
disk is a mechanical device.
• Like RAM, data in virtual memory becomes
inaccessible if the power fails.
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ROM
• Read-only memory (ROM) chips have programs
built into them at the factory. Unlike RAM chips,
ROM chips are not volatile and cannot be changed
by the user.
• ROM contains several sets of instructions:
– ROM bootstrap: tell the processor what to do
when you first turn on, or boot the computer.
– ROM BIOS (basic input/output system) : tell
the computer how to access the disk drives and
other peripheral devices.
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ROM
• BIOS is a small, but critical part of the
operating system that tells the computer
how to access the disk drives.
• When you turn on your computer, the CPU
performs the instructions in the ROM BIOS
to search the disk drive for the main
operating system files. The computer then
load these files into RAM and use them for
the remainder of the computing session. . 23
ROM variations
• PROM (programmable ROM): the user with
special equipment can store programs on it.
• EPROM (erasable PROM): it can be
programmed by the user and it can be
erased with a special device that applies
ultraviolet light.
• EEPROM (electronically EPROM): it can
be programmed and erased using electronic
impulses.
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CMOS
• A complementary metal-oxide semiconductor
(CMOS) chip contains essential information that is
required every time the computer system is turned
on.
• The chip supplies such information as the amount
of RAM, type of keyboard, mouse, monitor, and
disk drives.
• Unlike RAM, it is powered by a battery and does
not lose its contents when the power is turned off.
• Unlike ROM, its contents can be changed to
reflect changes in the computer system such as
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increased RAM and new hardware devices.
part 3
MICROPROCESSOR
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Introduction
• In a microcomputer system, the central processing
unit (CPU) or processor is contained on a single
chip called the microprocessor.
• Typically, this microprocessor is contained within
a cartridge that plugs in to the system board.
• The microprocessor is the "brains" of the system.
It retrieves instructions and data from RAM,
processes those instructions, then places the
results back into RAM so they can be displayed or
stored.
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Introduction
• The central processing unit has two basic
components: the control unit and the
arithmetic-logic unit(ALU).
• What does a microprocessor look like?
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Arithmetic-Logic Unit
• The arithmetic-logic unit(ALU), performs two
types of operations—arithmetic and logical.
• Arithmetic operations are the fundamental math
operations: addition, subtraction, multiplication,
and division.
• Logical operations consist of comparisons. That is,
two pieces of data are compared to see whether
one is equal to (=), less than (<), or greater than (>)
the other.
• The ALU uses registers to hold data that is being
processed. In the ALU the result of an arithmetic
or logical operation is held temporarily in the
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accumulator, as shown in the following figure.
Control Unit
• The control unit tells the rest of the
computer system how to carry out a
program's instructions.
• It directs the movement of electronic signals
between memory –which temporarily holds
data, instructions, and processed
information—and the arithmetic-logic unit.
• It also directs these control signals between
the CPU and input and output devices.
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Control Unit
• The control unit retrieves each instruction in
sequence from RAM and places it in a special
instruction register.
• The control unit then interprets the instruction to
find out what needs to be done.
• According to its interpretation, the control unit
sends signals to the data bus to fetch data from
RAM, and to the arithmetic logic unit to perform a
process. We can see the role of control unit in the
following figure.
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Registers
• The control unit and ALU both contain registers.
• Registers are special high-speed circuitry areas
that temporarily store data during processing and
provide working area for computation.
• It could be said that main memory, which is
outside the processor, holds material that will be
used "a little bit later." Registers, which are
contained in the processor, hold material that is to
be processed immediately.
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Registers
• Data registers: nowadays computers use dozens of
data registers inside the CPU to speed up the
operations.
• Instruction register: stores instructions and later
interprets them, and executes them.
• Program counter: keeps track of the instruction
currently being executed. After execution of the
instruction, the counter is incremented to point to
the address of the next instruction in memory.
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The machine cycle
• The machine cycle comprises a series of
operations performed to execute a single program
instruction.
• It is the shortest interval in which an elementary
operation can take place within the processor.
• The machine cycle consists of two parts: an
instruction cycle, which fetches and decodes; and
an execution cycle, which executes and stores.
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The machine cycle
• In the instruction cycle, or I-cycle, the
control unit (1) fetches (gets) an instruction
from main memory and (2) decodes that
instruction (determines what it means). and
stores.
• During the execution cycle, or E-cycle, the
arithmetic/logic unit (3) executes the
instruction (performs the operation on the
data) and (4) stores the processed results in
a register.
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The machine cycle
• The following figures will show you how a
single instruction is processed.
• A detailed example is shown on page 88.
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CPU performance
• CPU speed is influenced by several factors
including clock rate, word size, cache, and
instruction set size.
• Specifications for these factors allow you to
compare different CPUs.
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Clock rate
• A computer contains a system clock that emits
pulses to establish the timing for all system
operations.
• The system clock sets the speed or "frequency" for
data transport and instruction execution.
• The time to complete an instruction cycle is
measured in megahertz (MHz), or millions of
instructions per second (MIPS).
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Word size
• Word size refers to the number of bits the
CPU can manipulate at one time.
• Word size is based on the size of the
registers in the CPU and the number of data
lines in the bus.
• For example, a CPU with an 8-bit word size
is referred to as an 8-bit processor, it has 8bit registers and manipulates 8 bits at a time.
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Cache
• Cache, sometimes called RAM cache or cache
memory, is special high-speed memory that gives
the CPU more rapid access to data.
• A high-speed CPU can execute an instruction so
quickly that it often waits for data to be delivered
from RAM; this slows down processing.
• The cache ensures that data is immediately
available whenever the CPU requests it.
• Most newer microprocessors have cache memory
built in.
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Cache
• As you begin a task, the computer anticipates what
data the CPU is likely to need and loads this data
into the cache area.
• When an instruction calls for data, the CPU first
checks to see if the required data is in the cache.
• If so, the CPU takes the data from the cache
instead of fetching it from RAM, which takes
longer. Refer to page 75 –76 for more.
• All other factors being equal, more cache means
faster processing.
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Types of microprocessor chips
• CISC chips: The most common type of
microprocessor is the complex instruction set
computer (CISC) chip. This design was
popularized by Intel and is the basis for their line
of microprocessors.
• RISC chips: reduced instruction set computer
(RISC) chips use fewer instructions. This design is
simpler and less costly than CISC chips.
Macintosh computers and many workstations use
RISC technology.
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Moore’s law
• In 1965, Gordon Moore, co-founder of chipproduction giant, Intel Corporation,
predicted that the number of transistors on a
chip would double every 18-24 months.
• ”Moore’s law” accurately predicted 30
years of chip development.
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part 4
INPUT DEVICES
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How is I/O hardware used by a
computer system?
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Different kinds of input
hardware
• Keyboard
• Pointing devices
– mouse
– Notebook Pointing devices(trackballs, track
points, and touch pad)
– Joystick
– Pen input
• Source-data entry devices
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Different kinds of input
hardware
• Source-data entry devices
–
–
–
–
–
–
Scanners
Voice-recognition devices
Audio/Video input devices
Digital cameras
Sensors
Human-biology input devices
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keyboard layout
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Functions of different keys
•
•
•
•
Standard typing keys
Cursor movement keys
Numeric keys
Function keys
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ergonomic keyboard
• Ergonomics is the study of the physical
relationships between people and their work
environment; that is, it is the science of designing
equipment for a safe and comfortable environment.
• Ergonomics deals with designing efficient and
safe chairs, desks, and lights. It also recommends
safe viewing distances from monitors.
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Pointing device——mouse
• The mouse is the most widely used pointing
device because it takes full advantage of a
graphical user interface.
• Designed to fit comfortably under the palm
of your hand, a mouse is an input device
that is used to control the movement of the
pointer on the screen and to make selections
from the screen.
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Pointing device——mouse
• Mouse types
– A mouse that has a rubber or a metal ball on its
underside is called a mechanical mouse.
– Another type of mouse, called an optical mouse,
has no moving mechanical p0arts inside;
instead it uses devices that emit light to detect
the mouse’s movement.
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Notebook Pointing devices
• track point (pointing stick)
• track ball
• touch pad
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Joystick
• A joystick is a vertical lever mounted on a
base.
• You move the lever in different directions
to control the actions of a vehicle or player.
• The lever usually includes buttons called
triggers that you can press to activate
certain events.
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Pen input
• Many input devices use an electronic pen
instead of a keyboard or mouse for input.
• Some of these devices require you to point
to onscreen objects with the pen; others
allow you to input data using drawings,
handwriting, and other symbols that are
written with the pen on a surface.
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Pen Input——Light pen
• A light pen is a handheld input device that contains
a light source or can detect light.
• You press the light pen against the surface of the
screen or point the light pen at the screen and then
press a button on the pen.
• Light pens are used in applications where desktop
space is limited such as in the health-care field or
when a wide variety of people use the application,
such as electronic voting.
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Pen Input——Pen computing
• Many handheld computers also allow you to
input data using an electronic pen.
• The pen (also called a stylus) looks like a
ballpoint pen but uses an electronic head
instead of ink.
• Pen computers use handwriting recognition
software that translates the letters and
symbols used in handwriting into character
data that the computer can use.
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Pen Input——Graphics tablet
• A graphics tablet, also called a digitizer or
digitizing tablet, consists of a flat, rectangular,
electronic plastic board used to input drawings,
sketches, or other graphical data.
• Each location on the graphics tablet corresponds to
a specific location on the screen.
• When you draw on the tablet with either an
electronic pen or a puck, the tablet detects and
converts the movements into digital signals that are
sent into the computer.
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Source-data entry devices
• Source-data input devices do not require
keystrokes to input data to the computer.
• In other words, data is entered from as close
to the source as possible; people do not need
to act as typing intermediaries.
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Scanning devices——scanners
• An optical scanner, usually simply called a
scanner, is a light-sensing input device that
reads printed text and graphics and then
translates the results into a form the
computer can use.
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Scanning devices——Bar code
readers
• A bar code reader uses laser beams to read
bar codes.
• A bar code is an identification code that
consists of a set of vertical lines and spaces
of different widths.
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Character and mark
recognition devices
• OCR
• Optical character recognition uses a device
that reads special OCR character sets called
OCR fonts, as well as typewriter and
computer-printed characters, and converts
them into machine readable form.
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Character and mark
recognition devices
• OMR
• Optical mark recognition uses a device that
reads pencil marks and converts them into
computer-usable form.
• Well-known examples are the OMR
technology used to read the College
Entrance Examination, and TOEFL(Test of
English as a Foreign Language),
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GRE(Graduate Record Examination).
Character and mark
recognition devices
• MICR
• In magnetic-ink character recognition, a
scanner translates the magnetically charged
numbers printed at the bottom of bank
checks and deposit slips.
• MICR characters, which are printed with
magnetized ink, are read by MICR
equipment, producing a digitized signal.
This signal is used by a bank’s reader/sorter
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machine to sort checks.
Voice-recognition devices
• A voice recognition system, using a
microphone (or a telephone) as an input
device, converts a person’s speech into
digital code by comparing the electrical
patterns produced by the speaker’s voice
with a set of prerecorded patterns stored in
the computer.
• Today the most widely used system is
IBM’s ViaVoice.
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Audio input devices
• An audio input device records or plays
analog sound and translates it for digital
storage and processing.
• Microphone, sound card, MIDI keyboard are
some typical audio input devices.
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Video input devices
• Video input or video capture is the process of
entering a full-motion recording into a computer
and storing the video on a hard disk or some other
medium.
– video camera/VCR + video capture card
– digital video camera
• A video conference is a meeting between two or
more geographically separated individuals who use
a network or the Internet to transmit audio and
video data.
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Digital cameras
• A digital camera allows you to take pictures
and store the photographed images digitally
instead of on traditional film.
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Sensors
• A sensor is a type of input device that
collects specific kinds of data directly from
the environment and transmits it to a
computer.
• Sensors can be used for detecting all kinds
of things: speed, movement, weight,
pressure, temperature, humidity, wind,
current, fog, gas, smoke, light, shapes,
images, and so on.
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Human-biology input devices
• Biometric systems: Biometric security devices
identify a person through a fingerprint, voice
intonation, or other biological characteristics.
• Line-of-sight systems: Line-of-sight systems
enable a person to use his or her eyes to point at
the screen, a technology that allows users with
physical disabilities to direct a computer.
• Cyber gloves and body suits: Special gloves and
body suits—often used in conjunction with “virtual
reality,” or the computer-generated simulation of
reality—use sensors to detect body movements. 70
part 5
OUTPUT DEVICES
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Monitors and video cards
• Monitors are the most widely used out
device which are used to create softcopy
output.
• Monitors run under the control of a video
card plugged into an expansion slot on the
system board.
• The adapter allows information to leave the
computer and appear on the monitor.
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Monitors and video cards
• The video card comes with its own RAM,
called VRAM, or video RAM. VRAM
controls the resolution of images displayed
on the monitor, as well as the number of
colors and the speed at which the images are
displayed.
• The size of a screen is measured diagonally
form corner to corner in inches, just like
television screens.
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Different monitors
• The cathode-ray tube(CRT) is a vacuum
tube used as a display screen in a computer.
• The CRT’s screen display is made up of
small picture elements(dots), called pixels
for short.
• A pixel is the smallest unit on the screen that
can be turned on or off or made different
shades.
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Different monitors
• A stream of bits defining the image is sent from
the computer to the CRT’s electron gun, where
electrons are activated according to the bit patterns.
• The front of the CRT screen is coated inside with
phosphor.
• When a beam of electrons from the electron gun
(deflected through a yoke) hits the phosphor, it
lights up selected pixels to generate an image on
the screen.
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Different monitors
• Compared to CRTs, flat-panel displays are much
thinner, weigh less, and consume less power.
• A current limitation is cost: an LCD for a desktop
microcomputer costs 2-3 times as much as an
equivalent monitor based on CRT technology.
• Also, flat-panel displayed images are not always as
good as CRT images, and flat-panel images cannot
be clearly viewed from an angle.
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Different monitors
• Flat panel displays consist of two plates of
glass separated by a substance that may be
activated in particular ways.
• Flat-panel displays may be characterized in
terms of (1) the substance between the plates
of glass and (2) the arrangement of the
transistors in the screens.
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Different monitors
• A liquid crystal display (LCD) consists of a
substance called liquid crystal, the molecules of
which line up in a particular way.
• Under an applied voltage, the molecular alignment
is disturbed, which changes the optical properties
of the liquid crystal in the affected area.
• As a result, light—usually backlighting behind the
screen—is blocked or allowed through to create an
image.
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Screen clarity
• Whether for CRT or flat-panel, screen
clarity depends on three qualities: resolution,
dot pitch, and refresh rate.
• The clarity or sharpness of a display screen
is called its resolution; the more pixels there
are per square inch, the better the resolution.
• Resolution is expressed in terms of the
formula：
columns of pixels × rows of pixels
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Screen clarity
• Dot pitch is the amount of space between pixels;
the closer the dots, the crisper the image.
• A .28 dot pitch means dots are 28/100ths of a
millimeter apart.
• Generally, a dot pitch of less than .31 will provide
clear images.
• Multimedia and desktop publishing users typically
use .25 mm or less dot pitch monitors.
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Screen clarity
• Refresh rate is the number of times per second that
the pixels are recharged so that their glow remains
bright.
• Refresh is necessary because the phosphors hold
their glow for just a fraction of a second.
• The higher the refresh rate, the more solid the
image looks on the screen –that is, it doesn’t
flicker.
• The refresh rate should be at least 72 Hz(Hertz).
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screen color
• Display screen can be either monochrome or
color.
– Monochrome display screens display only one
color on a background—usually black on white,
amber on black, or green on black. The number
of shades of the one color that the monitor can
display is referred to as gray-scale.
– Color display screens, also called RGB monitors
(for red, green, blue), can display between 16
colors and 16.7 million colors, depending on
their type. The number of colors is referred to as
the color depths, or bit depth.
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screen color
• There are different standards for monitors,
and they support different color depths.
– VGA, for video graphics array, will support 16
to 256 colors depending on resolution.
– SVGA, for super video graphics array, will
support 256 colors at higher resolution than
VGA.
– Also referred to as high-resolution display,
XGA, for extended graphics array, supports up
to 16.7 million colors at a resolution of
1024×768 pixels.
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Printers
• A printer is an output device that produces
text and graphics on a physical medium such
as paper or transparency film.
• Printed information is called hard copy
because the information exists physically
and is a more permanent form of output than
that presented on a display device (soft
copy).
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different kinds of printers
• An ink-jet printer sprays small droplets of
ink at high speed onto the surface of the
paper.
• This process not only produces a letterquality image but also permits printing to be
done in a variety of colors.
85
different kinds of printers
• The laser printer uses a technology similar
to that used in a photocopying machine. It
uses a laser beam to produce images with
excellent letter and graphics quality.
86
different kinds of printers
• A thermal printer uses heat elements to
produce images on heat-sensitive paper. It
was originally used in scientific labs to
record data, however, nowadays, it has been
used to produce very high quality color
artwork and text.
87
different kinds of printers
• Dot-matrix printers form characters or
images using a series of small pins on a print
head.
• Once the most widely used microcomputer
printer, dot-matrix printers are inexpensive
and reliable but quite noisy.
88
Plotters
• Plotters are special-purpose output devices
for producing bar charts, maps, architectural
drawings, and even three-dimensional
illustrations.
• Plotters can produce high-quality multicolor
documents and also documents that are
larger than most printers can handle.
• Two basic types of plotters are pen plotters
and electrostatic plotters.
89
Audio/voice output devices
• Audio is music, speech, or any other sound.
• Audio output devices are the components of
a computer that produce music, speech, or
other sounds, such as beeps.
• Two commonly used audio output devices
are speakers and headsets(headphones).
90
other output devices
• A data projector takes the image that
displays on a computer screen and projects it
onto a screen so that an audience of people
can see the image clearly.
• Data projectors can be large devices
attached to a ceiling or wall in an auditorium,
or they can be small portable devices.
91
other output devices
• A fax machine is a device that transmits and
receives documents over telephone lines.
• The documents can contain text, drawings,
or photographs, or can be handwritten.
• When sent or received via a fax machine,
these documents are known as faxes.
92
other output devices
• A multifunction device is a single piece of
equipment that looks like a copy machine
but provides the functionality of a printer,
scanner, copy machine, and perhaps a fax
machine.
• Sometimes called a multifunction peripheral,
the features of multifunction devices vary
widely.
93
Devices that do both I and O
• A monitor that has a touch-sensitive panel on the
screen is called a touch screen.
• You interact with the computer by touching areas
of the screen with your finger, which acts as an
input device.
• Because they require a lot of arm movement, touch
screens are not used to enter large amounts of data.
• Instead you touch words, pictures, numbers, or
locations identified on the screen.
94
Devices that do both I and O
• People working on a large computer system
are usually connected to the main, or host,
computer via terminals.
• A terminal is an input/output device that
uses a keyboard for input and a monitor for
output.
95
Devices that do both I and O
• Terminals can be either dumb or intelligent.
– A dumb terminal can be used only to input data
and receive information from a computer
system; it cannot do any processing on its own.
– In addition to a monitor and keyboard, an
intelligent terminal also has memory and a
processor that has the capability of performing
some functions independent of the host
computer.
96
Devices that do both I and O
• Some terminals are built specifically to accomplish
certain tasks—for example, the point-of-sale
terminal and the automated(automatic) teller
machine(ATM).
– A POS terminal combines the input capabilities of a
cash register-type keypad, an optical scanner for reading
price tags, and/or a magnetic stripe reader for reading
credit cards with the output capabilities of a monitor and
a receipt printer.
– The ATM reads the encoded magnetic stripe on the
ATM card and provides output in the form of display on
a monitor and printed records of transactions.
97
part 6
SECONDARY STORAGE
DEVICES
98
Storage Hierarchy
99
Floppy discs
• A floppy disk, or diskette, is a portable,
inexpensive storage medium that consists of
a thin, circular, flexible plastic disk with a
magnetic coating enclosed in square-shaped
plastic shell.
• The most widely used floppy disk is the 1.44
MB 3.5-inch disk.
100
Characteristics of a floppy disk
• A floppy disk is a type of a magnetic disk, which
means it uses magnetic patterns to store items such
as data, instructions, and information on the disk’s
surface.
• Most magnetic disks are read/write storage media;
that is, you can access (read) data from and place
(write) data on a magnetic disk any number of
times, just as you can with an audiocassette tape.
101
Characteristics of a floppy disk
• Formatting is the process of preparing a disk
(floppy disk or hard disk) for reading and writing
by organizing the disk into storage locations called
tracks and sectors.
• A track is a narrow recording band that forms a
full circle on the surface of the disk.
• The disk’s storage locations then are divided into
pie-shaped sections, which break the tracks into
small arcs called sectors.
• A sector is capable of holding 512 bytes of data.
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Characteristics of a floppy disk
• If you are using the Windows system, the
formatting process also defines the file
allocation table(FAT), which is a table of
information used to locate files on a disk.
• The FAT is like a library card catalog for
your disk that contains a listing of all files,
file types, and locations.
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high-capacity floppy disk
• Several manufacturers have high-capacity
floppy disk drives that use disks with
capacities of 100MB and greater.
• The three best known are：
– Zip disks(100MB/250MB)
– SuperDisks(120MB)
– HiFD disks(200MB).
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Hard discs
• A hard disk usually consists of several inflexible,
circular disks, called platters, on which items are
stored electronically.
• A platter in a hard disk is made of aluminum, glass,
or ceramic and is coated with a material that allows
items to be magnetically recorded on its surface.
• On hard disks, the platters, the read/write heads,
and the mechanism for moving the heads, and the
mechanism for moving the heads across the
surface of the disk are enclosed in an airtight,
sealed case that protects the platters from
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contamination.
Track: a concentric circle on
the surface of a platter.
Sector: a
section of a
track.
Cluster: a group of
sectors.
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Step 3: The head
moves to the FAT
to determine the
current or new
location of the
data.
Step 1: The circuit
board enables the
actuator and motor
to move.
Step 2: The motor
spins the platters.
Step 4: The actuator arm
moves head to the
correct location to read
or write data.
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How a hard disk drive works…
Characteristics of a hard disk
• magnetic disk
• two formatting steps, and possibly a third
process, called partitioning.
– The first format, called a low-lever format,
organizes both sides of each platter into tracks
and sectors to define where items will be stored
on the disk.
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Characteristics of a hard disk
• two formatting steps, and possibly a third
process, called partitioning.
– a high-level format command defines, among
other items, the file allocation table(FAT) for
each partition. Recall that the FAT is a table of
information used to locate files on a disk.
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Characteristics of a hard disk
• two formatting steps, and possibly a third
process, called partitioning.
– the hard disk can be divided into separate areas
called partitions by issuing a special operating
system command. Each partition functions as if
it were a separate hard disk drive.
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EIDE versus SCSI
• Two common types of hard disk
architectures are used in microcomputers:
EIDE and SCSI.
– EIDE, or Enhanced Integrate Drive Electronics,
refers to a type of hardware interface widely
used to connect hard disks and CD-ROM drives
to a PC via a bus.
– EIDE connects via a flat ribbon cable to an
expansion board called a host adapter, which
plugs into an expansion slot on the motherboard.
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EIDE versus SCSI
– With EIDE drives, the controller electronics are
contained on a printed circuit board within the
drive itself, so that the adapter is a fairly simple
circuit board.
– EIDE can attain data transfer rates up to 33 MB
per second.
– EIDE controllers also are referred to as ATA,
short for the AT Attachment, that integrates the
controller into the disk drive.
– Many versions of ATA exist, including ATA,
ATA-4, Ultra ATA, Ultra DMA, and ATA/66.112
EIDE versus SCSI
– SCSI(small computer system interface) is the
drive interface used on Mac computers and
high-end PCs, including multimedia
workstations and network servers.
– SCSI allows the connection of 7-15 peripheral
devices in a daisy chain hookup to a single
expansion board. SCSI-2 can attain transfer rate
of 20-40 MB per second; ultra 3 SCSI, 160MB
per second.
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Performance factors
• The rotational speed defines how fast the
disc is spinning.
• The seek time defines the time to move the
read/write head to the desired track where
the data are stored.
• The transfer time defines the time to move
data from the disk to the CPU/memory.
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USB Flash Drive
• A USB flash drive is a NAND-type flash memory
data storage device integrated with a USB
interface.
• USB flash drives are typically removable and
rewritable, much shorter than a floppy disk (1 to 4
inches or 2.5 to 10 cm), and weigh less than 2
ounces (60 g).
• Storage capacities typically range from 64 MB to
64 GB with steady improvements in size and price
per gigabyte. Some allow 1 million write or erase
cycles and have 10-year data retention, connected
by USB 1.1 or USB 2.0.
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Optical discs
• Optical disks use laser technology to store data.
• In optical-disk technology, a laser beam alters the
surface of a plastic or metallic disk to represent
data.
• The 1s and 0s are represented by flat areas called
lands and bumpy areas called pits on the disk
surface.
• The disk is read by a laser that projects a tiny beam
of light on these areas.
• The amount of reflected light determines whether
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the area represents a 1 or a 0.
Different kinds of optical disks
• There are two common kinds of optical
disks: CD and DVD.
– CD(CD-ROM, CD-R, CD-RW)
– DVD(DVD-ROM, DVD-R, DVD-RAM, DVDRW)
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guidelines for the proper care
of optical discs
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Magnetic tapes
• Features of tapes:
– Sequential access(slow)
– Used almost exclusively for backup
– Can contain TBs of data
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part 7
Subsystem Interconnection
120
Introduction
• I/O between the CPU and peripheral
devices often involves a long path that
moves data over the expansion bus, slots,
cards, ports, and cables.
• The following figure is an overview of the
I/O architecture.
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Bus
• A bus connects the parts of the CPU to each other.
• It also links the CPU to various other components
on the system board.
• A bus is the data roadway along which bits travel.
• Such data pathways resemble a multilane highway.
The more lanes there are, the faster traffic can go
through.
• Similarly, the greater the capacity of a bus, the
more powerful and faster the operation. A 64-bit
bus has greater capacity than a 32-bit bus, for
example.
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Bus
• According to the equipment a bus connects,
a bus can be one of the following:
– Internal Bus : connecting different components
inside a device.
– System Bus : connecting CPU and memory.
– Expansion Bus: connecting CPU and peripheral
devices.
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System bus
• The CPU and memory are normally
connected by the three groups of system
buses: data bus, address bus and control bus.
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System bus
• The data bus is made of several wires, each
carrying 1 bit at a time. The number of wires
depends on the size of the word.
• The address bus allows access to a particular word
in memory. The number of wires in the address
bus depends on the address space of memory.
• The control bus carries communication between
the CPU and the memory. The number of wires
used in the control bus depends on the total
number of control commands a computer needs.
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Expansion bus——ISA
• The three principal expansion bus lines (or
"architectures" )are:
– Industry Standard Architecture (ISA) was
developed for the IBM Personal Computer.
First it was an 8-bit-wide data path; then it was
16 bits wide. Because of its slowness, it's
almost out of use today.
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Expansion bus——PCI
– Peripheral Component Interconnect (PCI) was
originally developed to meet the video demands
of graphical user interfaces.
– PCI is a high speed 32-bit or 64-bit bus that is
over 20 times faster than ISA buses.
– PCI bus has replaced ISA bus to connect the
CPU, memory, and expansion boards.
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Expansion bus——AGP
– Accelerated Graphics Port (AGP) is the newest
bus and over twice as fast as the PCI bus.
– While the PCI bus is used for a variety of
purposes, the AGP bus is dedicated to the
acceleration of graphics performance.
– Widely used for graphics and 3-D animations,
the AGP is replacing the PCI bus for the
transfer of video data.
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Expansion bus——PCI-E
• Peripheral Component Interconnect Express is
a computer expansion card interface format
introduced by Intel in 2004.
• PCI Express was designed to replace the generalpurpose PCI expansion bus, the high-end PCI-X
bus and the AGP graphics card interface.
• Unlike previous PC expansion interfaces, rather
than being a bus it is structured around point-topoint serial links called lanes.
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Expansion slots and cards
• On the main board, the expansion bus terminates
at an expansion slot.
• An expansion slot is a socket into which you can
plug a small circuit board called an expansion card.
• The expansion slots on mainframes,
minicomputers, and microcomputers provide a
way to connect a large variety of peripheral
devices.
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Expansion slots and cards
• Three types of expansion cards found in
most of today's computers are a video card,
a sound card, and an internal modem.
• A video card, also called video adapter or
graphics card, converts computer output
into a video signal that is sent through a
cable to the monitor, which displays an
image on the screen.
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Expansion slots and cards
• A sound card is used to enhance the soundgenerating capabilities of a personal computer by
allowing sound to be input through a microphone
and output through speakers.
• An internal modem is a communications device
that enables computer to communicate via
telephone lines or other means.
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Ports
• External devices such as a keyboard, monitor,
printer, mouse, and microphone, often are attached
by a cable to the system.
• The interface, or point of attachment, to the
system unit is called a port. Ports are sometimes
called “jacks” or “connectors” or “controllers” or
“interfaces”.
• A port is a socket on the outside of the system unit
that is connected by a bus to an expansion board
on the inside of the system unit or connected
directly to integrated circuitry on the motherboard.
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Ports
• Serial ports: Lines connected to a serial port, or
RS-232 port, send bits one after the other in a
single sequence, like cars on a one-lane highway.
• Serial lines are used to link equipment that is not
close by. They are used to connect a mouse,
keyboard, modem, and many other devices to the
system unit.
• Serial ports are usually called COM ports, for
communications.
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Ports
• Parallel ports: Lines connected to a parallel port
allow 8 bits to be transmitted simultaneously, like
cars on an eight-lane highway.
• Parallel lines move information faster than serial
lines do, but they can transmit information
efficiently only up to 15 feet(5.4 meters).
• Thus, parallel ports are used principally for
connecting printers.
135
Ports
• Video adapter ports: Video adapter ports are
used to connect the video display monitor
outside the computer to the video adapter
card inside the system unit.
136
Ports
• SCSI ports: Pronounced "scuzzy", a SCSI (short
for Small Computer System Interface) port
provides an interface for transferring data at high
speeds for up to seven or fifteen SCSI-compatible
devices, linked together in what is called a daisy
chain, along an extended cable.
• Daisy chain means the first SCSI device connects
to the computer, the second SCSI device connect
to the first SCSI device, and so on. SCSI devices
include external hard disk drives, magnetic-tape
backup units, scanners, and CD-ROM drives. 137
Ports
• Game ports: Game ports allow you to attach a
joystick or similar game-playing device to the
system unit.
• USB ports: Universal Serial Bus (USB) is a type
of port that allows you to connect up to 127
devices using only one port. For example, you can
use a USB port to connect a printer, modem,
joystick, and scanner to your computer. Most new
computers come with two USB ports.
138
Ports
139
part 8
BOOT PROCESS
140
Introduction
• The sequence of events that occurs between the
time you turn on a computer and the time it is
ready for you to issue commands is referred to as
the boot process.
• When you turn on a computer after it has been
powered off completely, you are performing a
cold boot.
• A warm boot, by contrast, is the process of
restarting, or resetting, a computer that already is
on.
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Boot process (1)
• The following 7 steps explain what occurs
during a cold boot for a personal computer
using the Windows system.
• (1). When you turn on your computer, the
power supply sends an electrical signal to
the motherboard and the other device
located in the system unit.
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Boot process (2)
• (2). The surge of electricity causes the CPU chip
to reset itself and look for the ROM chip(s) that
contains the BIOS.
• The BIOS, which stands for basic input/output
system, is firmware that contains the computer's
startup instructions.
• Recall that firmware consists of ROM chips that
contain permanently written instructions and data.
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Boot process (3)
• (3). The BIOS begins by executing a series of tests
to make sure the computer hardware is connected
properly and operating correctly.
• The tests, commonly called the power-on self test
(POST), check the various system components
such as the buses, system clock, expansion cards,
RAM chips, keyboard, floppy disk drive(s), and
hard disk.
• As the POST is performed, LEDs flicker on
devices such as the disk drives and keyboard,
several beeps sound, and messages display on the
monitor's screen.
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Boot process(4)
• (4). The results of the POST are compared with
data in a CMOS chip on the motherboard.
• Recall that the CMOS chip stores configuration
information about the computer, such as the
amount of memory; type of disk drives, keyboard,
and monitor; the current date and time; and other
startup information needed when the computer is
turned on.
• The CMOS chip is updated whenever new
components are installed.
• If any problems are found, the computer may beep,
display error messages, or cease operating—
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depending on the severity of the problem.
Boot process (5)
• (5). If the POST is completed successfully, the
BIOS looks for the boot program that loads the
operating system.
• Usually, it first looks in drive A (the designation
for a floppy disk drive).
• If an operating system disk is not inserted into
drive A, the BIOS looks in drive C, which is the
designation usually given to the first hard disk.
• If neither drive A nor drive C contain the boot
program, some computers look to the CD-ROM
drive.
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Boot process (6)
• (6). Once located, the boot program is
loaded into memory and executed.
• The boot program then loads the kernel of
the operating system into RAM. The
operating system takes control of the
computer.
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Boot process (7)
• (7). The operating system loads system
configuration information.
• In Windows, system configuration information is
contained in several files called the registry.
• Windows constantly accesses the registry during
the computer's operation for information such as
installed hardware and software devices and
individual user preferences for mouse speed,
passwords, and other user-specific information.
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Boot process
• For each hardware device identified in the registry,
such as the sound card, a CD-ROM or DVD-ROM
drive, or a scanner, the operating system loads a
device driver. Recall that a device driver is a
program that tells the operating system how to
communicate with a device.
• The remainder of the operating system is loaded
into RAM and the desktop and icons display on
the screen. The operating system executes
programs in the StartUp folder, which contains a
list of programs that open automatically when you
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boot your computer.
Boot process
• The following figure summarizes the 7
steps.
150
Objectives
• Identify the components in the system unit
and explain their functions.
• Differentiate the various types of memory.
• Explain how the CPU uses the four steps of
a machine cycle to process data.
• List the factors that affect CPU performance.
151
Objectives
• Describe the types of expansion slots and
expansion cards in the system unit.
• List the components necessary to connect a
peripheral device to a computer and
describe each components’ role.
• List the commonly used I/O and secondary
storage devices.
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Objectives
• Describe factors that affect the quality of a
monitor.
• Explain how data are stored on a
floppy/hard disk.
• Differentiate between low-level formatting
and high-level formatting of a hard disk.
• Explain the startup process for a personal
computer.
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That’s all for this chapter!
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